An example of a conventional non-contact type power transfer apparatus is described in Laid-open patent publication Hei 6-311658. In the apparatus described therein, a signal to detect whether a device body is mounted to a power-supply body is created from a signal output from a primary coil in such a way that the output of a primary side oscillation circuit is sufficiently suppressed.
The above-mentioned conventional non-contact type power transfer apparatus uses a timer as an intermittent drive/oscillation means to set the intermittent time for oscillation. Such a timer, however, requires a timer IC, which increases the cost of the parts significantly. Moreover, such a conventional apparatus provides a constant oscillation duration irrespective of fluctuations in the input voltage. Thus, if only a low voltage is applied due to power-supply conditions, for example, the detection signal level for the device body will be low, while if only a high voltage is applied, this signal level will be high. Thus, the operation of the conventional apparatus is unstable.